[CentOS] How can rpm "%{SUMMARY}" not be consistent?

Wed Nov 16 22:20:39 UTC 2011
Nicolas Thierry-Mieg <Nicolas.Thierry-Mieg at imag.fr>

Denniston, Todd A CIV NAVSURFWARCENDIV Crane wrote:
> At one time (in the mists of history, probably around RHEL 1|2) I
> thought there was a daily rpm cleanup task, but I can't find it on Cent
> 5 systems.

there is something in /etc/rc.sysinit, so it would happen on reboot:
$ grep rpm /etc/rc.sysinit
rm -f /var/lib/rpm/__db* &> /dev/null